This invention relates to shuttle cleaning of heat exchanger tubes and is an improvement over the concepts disclosed in the above-identified patents.
It is known from the above-identified patents to connect individual elongated cleaning element capturing cages or baskets to both ends of longitudinally extending tubes disposed in a heat exchanger housing. The tube ends are held in position at both ends by transverse tube sheets. The baskets are adapted to contain shuttleable cleaning elements, such as brushes. Fluid flowing in one direction through the tubes keeps the cleaning elements captured within their respective basket chambers, while the fluid discharges outwardly through slot-like openings in the basket walls. Upon reversal of fluid flow, the cleaning elements are forced out of their baskets and through the tubes to the baskets at the opposite tube ends to thereby perform a tube cleaning action.
Several ways have been suggested to mount the baskets in fluid flow communication with the tubes, which enter openings in the tube sheets. The inner basket ends have been press fit into the openings or into the tube ends themselves.
The present inventors' U.S. Pat. No. 4,415,022 entitled "Mounting For Heat Exchanger Tube Cleaner Capturing Devices" discloses another arrangement where the inner basket ends are provided with a collar which hangs from a flared lip on the tube end which is disposed beyond the outer tube sheet face.
In some instances, the above-mentioned basket mounting arrangements may be undesirable. For example, in high temperature heat exchanger applications, a sole press fit connection may not hold due to large temperature fluctuations to which the joint is subjected. In other instances, the specifications for the particular heat exchanger may call for unthreaded tube sheet openings or unflared tube ends, or other structure incompatible with previous mounts.
It is a task of the present invention to provide a mounting means for the cleaning element capturing baskets which does not depend solely on the aforementioned methods of connection but which nevertheless holds the baskets securely in place.
In accordance with the various aspects of the invention, a basket retaining plate is fixedly mounted, as by bolts or the like, outwardly of the tube sheet in an adjacent or proximate, generally parallel relationship to the outer face of the tube sheet. The retaining plate may be mounted either in spaced relationship from or in abutting relationship with the outer tube sheet face. The plate and its mount cooperate with the tube sheet to hold the baskets in fixed position relative to the tube sheet and tube ends, regardless of temperature changes. The outer capturing and holding portions of the baskets extend outwardly from the retaining plate. The baskets include central or intermediate portions which extend through openings in the plate and inner portions which terminate within the tube sheet openings. The baskets are fixedly secured against transverse shifting by a two-point support, one at the inner basket ends and one intermediate their ends. To hold the baskets in longitudinally fixed position, and in one embodiment, the basket intermediate portions are threaded to the retaining plate. In another embodiment, shoulders adjacent the inner basket ends engage the plate and tube sheet. The retaining plate may be of lesser diameter than the tube sheet and may be provided with unobstructed fluid flow openings between the baskets and basket-receiving openings.